1. Field of the Invention
The present invention relates generally to illuminating instrument panel gauges and, more particularly, to illuminating instrument panel gauges having movable indicators.
2. Description of the Related Art
Illuminating instrument panel gauges for automobiles, usually placed in the dash, most often include those with movable indicators or pointers to show the status of various operations of the automobile. Such instrument panel gauges include speedometers, gas gauges, engine temperature gauges, and tachometers. FIG. 1 shows a cross sectional side view of typical current illuminating instrument panel gauge 10. Illuminating instrument panel gauge 10 has front side 12 facing the viewer (represented by eye 13) and back side 14 positioned away from the viewer and includes light source 16 at back side 14 of the gauge, overlay 18 covering light source 16, yet allowing some light to illuminate the gauge, transparent gauge cover 20 in front of and spaced apart from overlay 18, and at least one movable indicator 23 between overlay 18 and gauge cover 20. Gauge cover 20 has first surface 21 facing the viewer and second surface 22 opposite first surface 21. Overlay 18 has front surface 24 which is sometimes referred to as the "subdial surface" upon which graphics 26 are placed which correspond to movable indicator 23. For example, for a speedometer, the graphics would include 10, 20, 30, 40 (mph) and so on, and the movable indicator would point to the number representing the current speed.
Typical instrument panel gauge 10 also includes light-impervious brow 28 which reduces the amount of reflection from the instrument panel gauge to the viewer's eyes. For example, ambient light (e.g., from the sun), shown as arrow 30, passes through windshield 32 and hits brow 28. Without brow 28, the light would hit gauge cover 20 and some of the light would reflect back into the viewer's eyes, impairing the viewer's vision.
Brow 28 is also present to reduce the amount of reflectance caused by light-colored objects inside the passenger compartment of the automobile. For example, when the viewer wears light-colored clothing, light from the clothing (represented by arrow 34) is reflected by gauge cover 20. This occurrence is often referred to as the "white shirt syndrome". Because of the angle of gauge cover 20 and the position of brow 28, much of the reflection from the clothing (represented by 35) is projected toward brow 28 and not seen by the viewer.
Brows, such as brow 28, however, are cumbersome in design and require a substantial amount of material to construct and add weight to the automobile. It would be desirable to control the instrument panel gauge reflections without the use of a brow in order to provide more automobile design flexibility (both functionally and aesthetically) and to save on material cost and weight of the automobile.
Another problem with current instrument panel gauges, such as instrument panel gauge 10 shown in FIG. 1, is the reduction in clarity of the graphics because the graphics are on the subdial surface. When illuminated, the light source in the instrument panel gauge improves the clarity of the graphics, however a loss in graphics clarity is experienced when the panel is not illuminated, which is often the case during the day. For example, when the gauge cover is clear (or 100% transmitting), around 8% of normal daylight reflects back to the viewer (about 4% from first surface 21 of the gauge cover and about 4% from second surface 22 of the gauge cover). This leaves only about 92% of the normal daylight passing through to subdial surface 24.
If subdial surface 24 is reflective, then some of the light striking the subdial surface is reflected back to the viewer with another approximate 8% loss of light through the gauge cover again. When the subdial surface is about 80% reflective, only about 67% of the original light finally reaches the viewer's eyes. In summary, a greatly reduced level of original light (about 67%) finally reaches the viewer to provide an image of the graphics. The loss of light results in diminished clarity of the graphics to the viewer.
It is, therefore, one object of the present invention to provide an illuminating instrument panel gauge with a movable indicator which has a reduced level of reflections emitting from the gauge cover.
It is another object of the present invention to provide an illuminating instrument panel gauge with a movable indicator which presents more design flexibility than previous illuminating instrument panel gauges.
It is yet another object of the present invention to provide an illuminating instrument panel gauge with a movable indicator which does not require a brow.
It is still another object of the present invention to provide an illuminating instrument panel gauge with a movable indicator which has improved graphics clarity for the viewer relative to previous illuminating instrument panel gauges.